Radon is a gas that is produced by the radioactive decay of naturally occurring heavy nuclei , such as thorium and uranium . Radon gas can be breathed into the lungs , where it can decay further . The nucleus of a radon atom has a mass of 222 u, where u is an atomic mass unit Assume that the nucleus is at rest when it decays into a polonium nucleus with mass 218 u and a helium nucleus with mass 4 u (called an alpha particle ), releasing 5.59 MeV of energy . The polonium and helium nucleus are emitted in exactly opposite directions . What are the kinetic energies of the polonium nucleus and the helium nucleus ? What we know

a person with a mass of 106kg has a weight of 1060n

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form

bacteria that live on the ocean floor are sustained by phytoplankton. phytoplankton, microscopic marine photosynthetic organisms, have a vastly significant role to play not only in the marine food web of which they’re part of, but also on a more global scale. despite their infinitely small size in comparison to other marine organisms, these tiny creatures occupy an immensely important ecological niche: they are the foundation of the marine food web, and as primary producers, play key roles in supporting all other organisms in the marine environment, as well as in the regulation of the earth’s climate through the sequestration of carbon, oxygen production, and other related processes. phytoplankton account for roughly half of all global primary productivity; therefore, their significance extends far beyond the marine environment alone. there is an intriguing sense of irony in the realization that these tiny living beings that often live out their existence unnoticed and undetected by the rest of the world, have such a far-reaching impact on the lives of virtually all other living organisms on the planet, particularly on those in the marine environment. the world that we have become accustomed to has been and is continuously shaped by the workings of these miniscule yet vital “plants of the sea”.

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